It's not just the weather that's been heating up Harlem this summer

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HAMBURG, GERMANY - MARCH 18: Smith & Wesson Magnum guns are seen in a gun store on March 18, 2009 in Hamburg, Germany. The recent shooting in the German town of Winnenden that left 16 people dead has brought up the issue of gun control once again in public and media discussions in Germany, though most politicians insist that existing laws are sufficient. Germany has relatively strict gun ownership laws. (Photo illustration by Joern Pollex/Getty Images)

Updated at 4:45 PM EDT on Thursday, Aug 12, 2010

After more than a decade of decreasing crime rates, this summer has seen a slight but ominous reversal: shootings are up 4.5 percent across the city versus this time last year.

Northern Manhattan has seen the worst of it. The gunfight in Harlem this weekend -- during which a young man was shot and killed by cops while another man was riddled with 23 NYPD bullets -- has brought attention to the grim findings that shootings in northern Manhattan are up 59 percent from this time last year.

Some have blamed the rise in violent crime down on the economy. "Gangs flourish when the legitimate economy doesn't offer opportunities for those at the lower end of the social-class ladder," Northeastern University criminologist James Alan Fox told New York Magazine. "Misery loves company, and [New York] is not the only city that is experiencing a spike in youth-gang violence."

Police spokesman Paul Brown disagrees. "I can tell you generally, the problem has been essentially the same: young men with guns," he told NYMag. "When that ebbs and flows, we haven't seen a connection with the economy."

In any case, the economy may be indirectly impacting crime rates by decreasing the size of the police force. The NYPD maintained 41,000 officers in 2001 and is now around 35,000.

"The economy definitely has an effect," Councilman Peter Vallone, who chairs the city council's Public Safety Committee, told the magazine. "We need to increase the force. In the local precincts you won't see the beat cop or the bicycle cop. You barely see anyone patrolling. I think it's because of the attitude that exists right now that the war on crime is over and we can be lax again."

New York Magazine's article on the summer's higher shooting rates comes just a few weeks after the New York Times reported the city's record-high marijuana arrest rates. A NYPD spokesman told NBCNewYork that stopping small-scale crime like marijuana dealing helps prevent larger-scale crime, a theory referred to as the "Broken Windows" policy among criminologists.

Others are skeptical of this opinion. A report by Professors Bernard E. Harcourt and Jens Ludwig of the University of Chicago and Georgetown University argues that there is no confirmed correlation between increased marijuana arrests and a decrease in organized crime.

"Though shootings are up 4.5% across the city, we can not attribute it to any specific factor," said a NYPD spokesperson in an emailed statement, when asked about a possible correlation between increased marijuana arrests and increased violent crime rates.